ALLEN LEBLANC LED A VIGOROUS LIFE as a young man growing up in Mossville, Louisiana. He had a sheet-rocking business, drove trucks, and worked at the Conoco oil refinery. He helped his mother and stepfather run their nightclub, where Tina Turner and James Brown used to play. He also helped out at home with his five children, and he would paint, fix broken windows, and mow lawns for neighbors who couldn’t afford to maintain their houses. Now, at 71, LeBlanc is on disability, and for most of the last decade he has refused to leave his house. Seizures, liver problems, a stroke, tremors, insomnia, fatigue, and depression plague him. He can no longer drive, and he can’t walk from his front door to the sidewalk without collapsing.

LeBlanc attributes his debilitation not to heredity or unhealthy habits but to the toxic emissions from industrial plants that have proliferated in the neighboring town of Westlake. Just beyond the curtain of pines and cypress trees surrounding Mossville sits an oil refinery, several petrochemical plants, and one of the country’s largest concentrations of manufacturers of vinyl chloride, a main ingredient in polyvinyl chloride, the plastic known as PVC. As a matter of course — and most often within permitted levels — these facilities emit millions of pounds of toxins into the air, water, and soil each year. “Living here has messed me up,” LeBlanc said. Although his appearance was disheveled, he spoke clearly and coherently, upright in his chair. “If I could have another life, I’d take it. This one ain’t worth 10 cents to me,” he said in his thick Louisiana drawl. “I’d like to do things for myself again — I’d give everything I’ve got for that.”

LeBlanc has known for more than 15 years that his body courses with toxins. In 1998 a group of local residents who organized under the name MEAN, Mossville Environmental Action Now, with the help of Greenpeace fought skillfully and hard to convince a federal agency within the Centers for Disease Control and Prevention to conduct toxicological testing. The Agency for Toxic Substances and Disease Registry, ATSDR, drew the blood of 28 Mossville inhabitants, including LeBlanc. The screening was for dioxins and dioxin-like compounds, a category comprising some of the most hazardous chemicals known to science. These highly toxic substances are formed when chlorine or a material containing chlorine is exposed to high temperatures — as happens in manufacturing vinyl chloride and other substances made in Westlake. The health effects of dioxins in humans can include cancer, damage to the reproductive system, impairment of the immune system, and disruption of normal hormone functions, which can lead to diseases such as diabetes. Dioxins are resistant to metabolism, so they can build up in the body, wreaking havoc for years.

The community’s toxicology results were staggering: The average dioxin level among the Mossville cohort was triple that of the general U.S. population. The median exceeded the country’s 95th percentile. As Kenneth Orloff, an ATSDR toxicologist who oversaw the study, told the Times-Picayune at the time, “I’m not aware of any other sites where we have found dioxin elevations of this magnitude.” The Mossville cohort’s dioxin rates were among the highest ever recorded in the country. LeBlanc said that when he got his results, “It was like someone put a bullet to me.”

Now, LeBlanc may lose his community as well. Sasol, a South African fuels company that wants to expand its massive petrochemical plant in Mossville, has issued buyout offers to almost everyone in town. For decades Mossville’s people have struggled to get answers about the toxins in their blood. In their fight they’ve been shut out not only by the petrochemical companies and elected leaders but also the very public health institutions meant to safeguard citizens from hazardous substances. Today, most of these families see no option other than taking the money and getting out while they still can.

LEBLANC AND I SAT IN PLASTIC CHAIRS on his sloping front porch. As we spoke, the shredded screen over the front window fluttered in the hot wind. LeBlanc was bedraggled. He had stopped bathing, he said, because when he washes in water from the tap, his skin peels away. Instead, he occasionally gives himself a sponge bath with alcohol. His hair and beard, which both have gone white, frizzed unkempt around his heavily creased, still handsome face. He no longer clips his fingernails or brushes his teeth because he doesn’t see the point. In the swooning heat, most days he dons the same dingy white T-shirt with a Fanta logo over his left breast and thin cotton pajama pants.

The ATSDR dioxin findings seemed to indicate a causal link between residents’ ailments and hazardous plant emissions. This didn’t surprise LeBlanc. Three generations of his family have spent much of their lives in Mossville. LeBlanc and his younger sister, Judy Montgomery, who lives nearby and takes care of him, can count more than a dozen family members and friends who have had cancer, many who have died from the disease. Among them is Valery, Montgomery’s father and LeBlanc’s stepfather, who has had prostate cancer, as have two of their uncles; an aunt died of ovarian cancer; a family friend’s son and father both had terminal throat cancer. And there is the abundance of other diseases. Yola, LeBlanc and Montgomery’s mother, had such acute diabetes that she frequently fell into insulin comas. She died of cardiac failure five years ago. Montgomery’s husband was diabetic. Both Montgomery and her daughter, Germaine Gauthia, who’s 37, have thyroid conditions and Gauthia has acute hypoglycemia. Both women struggle with their size. Montgomery, who’s just over 5 feet tall, weighs 230 pounds. Gauthia has always been heavy and now weighs more than 300 pounds. In her 20s Gauthia endured four miscarriages, and for years has suffered memory problems, as has her mother. Like LeBlanc, Gauthia has a chronic skin condition that worsens when she bathes in Mossville’s tap water. Her two children, now teenagers, have respiratory ailments. Her son has had learning disabilities and her daughter regularly breaks out with rashes on her stomach, face, arms, and legs — and open sores on her legs and ankles. “We’ve been asking for a health clinic for years,” Montgomery said, one with toxicologists who can diagnose and treat their ailments. “We need to know what’s going on, you see.”

The inhabitants of Mossville should have found a natural ally in the community of Westlake, which nestles even closer to many of the plants and is therefore vulnerable to the same pollution. Many people in both towns are sick with chronic conditions, but Westlake’s whiter, wealthier residents, a good share of whom work at the neighboring industrial facilities, have never joined the fight. While most people in Mossville blame the plants for their ailments, many Westlake residents have a different take. Of the people I interviewed, some emphatically denied a link between chronic disease and plant emissions while others said they’d never given it much thought and hoped it wasn’t true. Another, a man undergoing cancer treatment, said pollution might play a role in his disease but didn’t believe Westlake was any more polluted than other places.

“Do we have an inordinate amount of risk from the industries in southwest Louisiana? Absolutely not,” said Hal McMillin, an elected parish-level representative of Mossville and parts of Westlake for the past 16 years. He worked at the Conoco plant (now Phillips 66) for 23 years before getting into politics. When I inquired whether he had any chronic diseases, McMillin refused to answer. “It’s inappropriate of you to ask about my health.”